1. Field
The present disclosure relates to a tire vulcanizing device, more specifically of the type in which the part intended to form the tread of the tire is divided into several segments that can be moved radially in relation to the axis of the mold. In this type of vulcanizing device, the space for molding the exterior surface of the tire is defined by two shells, each one molding one sidewall, and by a ring of segments which mold the tread, these components together forming a curing mold.
2. Description of Related Art
Vulcanizing devices vulcanize the tire by applying pressure and heat energy to a green form of tire. Vulcanizing devices of the segmented type are made as several components which are assembled and driven with suitable dynamics in relation to the curing press.
The methods used for radially closing the segments onto the green form of the tire often involve closing the segments by sliding along the internal surface of a conical closure ring. Of the vulcanizing devices that employ such a conical closure ring those comprising molds referred to as container molds, in which the bottom shell is fixed and the molding cavity is closed by first of all bringing the top shell that molds the sidewall into contact with the green tire, this movement being initiated by the top plate of the container, then bringing the segments into contact with the green tire, are preferred for reasons of ease of access to the molding space when loading and unloading the tire. At the time of opening the mold, the segments accompany the top shell as the latter is lifted.
A container-type curing mold of this kind is described in U.S. Pat. No. 3,779,677. The mold comprises two lateral shells used for molding a sidewall of the tire and a peripheral ring comprising elements for molding the tread, this ring being divided into several segments having lateral faces perpendicular to the axis of the mold and radial transverse faces. The mold is closed by bringing the lateral shells axially closer together and then by moving the segments radially towards the axis of the mold. The radial movement of the segments is performed by a conical closure ring set in motion by the top plate of the press. The closure ring on its radially internal face comprises several T-shaped components, each being made to slide in a channel having an inclined guide surface of corresponding shape made on the radially external surface of a mold segment. Pivoting coupling elements connect the mobile plate that supports the top shell to the segments allowing these to move axially with the plate and to slide radially in radial slots of the plate.
Another example of a segmented vulcanizing device operating on the same principle as that of the previous document is described in document EP-0 170 109, the conical closure plate comprising, on its radially internal surface, guide grooves in which correspondingly shaped coupling pieces borne by the segments of the mold slide. Prismatic coupling elements connect the top faces of the segments to the mobile plate allowing the segments to move axially with the plate and to slide radially in correspondingly shaped prismatic guides belonging to the plate.
The major disadvantage with these vulcanizing devices is that the segments actuating assembly is dedicated to a specific mold, the parts of the device being machined to suit a fixed number of segments each having a predetermined angle and an amplitude of edge cutout which is dictated by the pattern and the circumference of the tire that is to be vulcanized. More particularly, the closure rings of the prior art are equipped with slide ways fixed to the radially internal wall of the ring to collaborate with a given number of mold segments and a pre-established angular positioning thereof. What is more, the mobile upper plate is machined to form the guide parts for returning the segments, these parts being dictated by the number and position of the mold segments. Thus, the closure ring and top plate of the prior art are permanently set up and suited to just one vulcanizing mold. This makes manufacture of the ring and of the plate of the vulcanizing device expensive while at the same time restricting their use to a restricted number of tire types.
Also known is document WO 2010/019134 in the name of the applicant company which proposes a vulcanizing device comprising elements for the attachment of the several adjacent half-segments, the attachment elements being produced in such a way as to be fitted to the periphery of each closure half-ring. However, this solution is specific to a vulcanizing device the closing and opening system of which involves the use of thrusting springs that push each half-segment. That document cannot provide a solution for optimizing the structure of molds of the container type in which each segment needs to be connected to the mobile plate and guided in its radial movement with respect thereto and at the same time able to collaborate with a closure ring.